Shinka no Mi might best be described as a parody of isekai stories with ridiculous, almost absurd, humor. Seiichi eats Seeds of Evolution, which allow him to grow stronger, and he also was given an ability to gain skill cards and a book containing the knowledge and life experiences of his defeated foes. Through this ability, he's able to see things from a more nuanced perspective and empathize with the opponents he's killed. The manga also seems like it's slowly piecing together events from the past which will probably lead to Seiichi learning some deep, dark hidden truth about the country or something.
Other than that, I guess what set's this manga apart from other isekai stories is that the first girl in his harem is a gorilla (or technically a Kaiser Kong). True, she spends a good portion of her time in her traditionally-attractive human form, but she also spends a decent amount of time in her gorilla form. I would honestly prefer it if she didn't have the human form at all. It doesn't add anything worthwhile to the story and it detracts from the sentiment that love can transcend physical appearance. Each story arc could probably be split into the stories of how the different girls get added to his harem. With the first girl being the gorilla Salia (ch. 1-5) and the second girl being the misfortune magnet Altria (ch. 6-14). They've now started a new story arc, and since it's still in its nascent stages, it may be too early to guess who the new harem recruit will be. The way I see it, there are two candidates: the adorable dog-eared girl May and the donkey Lulune (not "donkey-eared," just "donkey"). My best guess is that it'll be the donkey, 'cause that's just how this manga do.
[Reviewed at chapter 15]